Cancers occur and progress due to loss of both cell cycle and apoptotic controls. Currently, cancer chemotherapies center on the use of cytotoxic agents, which kill cancer cells but do not prevent them from dividing. This approach is often insufficient to control the rapid expansion of cancer cells during aggressive tumor growth and relapse. No anti-cancer compounds are currently available that also selectively inhibit the cell cycle. Consequently devastating cancers such as multiple myeloma are generally fatal.